Penelope Cruz hits right number

'Nine' actress nervous before recording song

The Spanish actress was so intimidated by the thought of singing professionally for the first time in “Nine” that on the day she was to hit the recording studio, she locked herself in a room and refused to speak to anyone.

“What you do in there is going to be on the record forever,” explains Cruz, who took home a supporting actress trophy for “Vicky Cristina Barcelona.” “It’s scary. I was just trying to breathe.”

Moviegoers will likely have the same reaction upon seeing Cruz’s turn as Carla, the mistress of “Nine’s” crisis-riddled film director Guido, played by Daniel Day-Lewis. Clad in a provocative pink corset and black thigh highs, Cruz, who as a teen trained in classical ballet, steams up the screen with Carla’s signature number, “A Call From the Vatican.”

If the rope-swinging performance was demanding — it took three consecutive 12-hour days to complete — tapping into what made her character tick was the easy part.

“Carla is many people in one,” Cruz says fondly. “Sometimes she’s a strong woman and sometimes a little fragile kid. When she’s in Guido’s environment, she feels something she doesn’t have in her own life — magic.”

With only a month off between “Nine” and a starring turn in “Broken Embraces,” her fourth film with mentor Pedro Almodovar, Cruz was so physically and emotionally drained that, outside of a brief cameo in the upcoming “Sex and the City” sequel, she has chosen not to work.

Yet the old fire is starting to burn again.

“You always feel like a student,” she says of acting. “I don’t think you ever get to a place where you feel, ‘I really know what this is about.’ You know more than at the beginning, but there is always so much more to learn.”